Blood pumps remain particularly useful for the treatment of cardiac disease and especially heart failure. Typically, blood pumps are implanted within a patient and connected to the patient's circulatory system as a ventricular assist device or, in some circumstances, as an artificial heart. However, the fragile nature of blood and the absolute necessity of the pump's reliability have presented numerous obstacles to designing a more perfect blood pump.
For example, most blood pumps contain moving parts, such as an impeller, that force blood into and out of the pump housing. If these moving parts are not properly designed and adjusted, the blood passing through the pump can be damaged, causing hemolysis or thrombosis. Further, these moving parts can wear on each other, causing an increased likelihood of part failure and heat buildup that is imparted to the blood.
Two recent blood pump examples can be seen in U.S. Pat. No. 6,234,772 to Wampler, et al. and U.S. Pat. No. 6,250,880 to Woodard, et al. The Woodard patent illustrates a rotary blood pump that includes an impeller supported exclusively by a hydrodynamic bearing. The Wampler patent describes a rotary blood pump that includes both a hydrodynamic support bearing and a radial magnetic bearing that utilizes a repulsive magnetic force.
In the case of either patent, the impeller of the blood pump contains motor drive magnets disposed within the blades of the impeller. Electromagnets are positioned within the pump housing to generate a magnetic field that drives the rotation of the motor drive magnets and therefore the impeller.
Both blood pumps suffer from hydraulic inefficiencies due at least in part to the large, unconventional impeller blade geometry required for containing the motor rotor magnets. Further inefficiencies of these designs arise because of the natural attraction between the motor rotor magnets of the impeller and the back iron of the electromagnets. Additionally, these blood pump designs exclusively rely on hydrodynamic bearing for axial support, which can result in excessive shear forces that can damage the blood and cause medical complications in the patient's health.
In view of the above discussion, it is apparent that there is a need for a blood pump that overcomes the limitations of the prior art. Specifically, what is needed is a blood pump that reduces inefficiencies inherent in prior art pump designs that can lead to pump failure or blood damage.